A method and a device for controlling an exhaust gas aftertreatment system are known from German Patent 199 062 87. In the system described therein, a particle filter is used which filters out particles contained in the exhaust gas. This particle filter must be regenerated at regular intervals. To this end, provision is made for increasing the exhaust gas temperature and thereby initiating burnup of the particles. An oxidation catalytic converter is usually used to increase the exhaust gas temperature. For the regeneration, there is provision for the introduction of hydrocarbons into the exhaust gas, which then react in the oxidation catalytic converter and lead to an increase in the exhaust gas temperature.
Very high demands for effectiveness and availability are placed on such an exhaust gas aftertreatment system. The effectiveness of the oxidation catalytic converter decreases with its length of use. The degradation of the effectiveness is dependent on the quality of the oxidation layer, and above all on the prevailing operating states, and is thus unpredictable. In order to prevent failure and/or deterioration of the operation of the oxidation catalytic converter, and accordingly to recognize a possible increase in emissions, checking of the oxidation catalytic converter is necessary.